Physical-Chemical Properties of Articulated Rodlike Polymers
Final rept. 1 Mar 1981-28 Feb 1982
CARNEGIE-MELLON UNIV PITTSBURGH PA
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Photon correlation and absolute intensity light screening studies have been coupled with size exclusion chromatography, viscometry and spectroscopic studies to investigate several articulated polymers. The results show that the polymers investigated tend to form intermolecular aggregates in solution. The effect of these can be reduced in number by increased temperature, sonication and centrifugation, but not completely removed. Results on solutions so treated are presently being analyzed in terms of a quasi-two component mixture of large aggregates few in number and molecularly dissolved species. Phase equilibria studies show that articulated polymers can form nematogenic solutions with the tendency increased with decreasing content of non-rodlike comonomer, as expected. For reasons unknown in detail, SPBT copolymers more readily form nematogenic solutions than do SPBO copolymers--a possible explanation may rest with increased intermolecular aggregation with SPBO copolymers. The critical concentration cc for stability of the nematic phase appears to be increased for rodlike polymers in polyphosphoric acid, PPA, as compared with methane sulfonic acid, MSA. This may reflect complex formation with PPA, effectively increasing the chain diameter. Mixtures of a nematogenic rodlike chain and an isotropic articulated chain exhibit depressed cc, as expected. Nonetheless, physical separation of the phases appears to be very difficult with the system studied thus far. Rheological data including measurements of the creep, recovery and dynamic compliances on solutions of an articulated rodlike copolymer in MSA are interpreted in terms of interchain association that is susceptible to cleavage and reformation in flow.
- Polymer Chemistry
- Atomic and Molecular Physics and Spectroscopy